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Wednesday, August 14, 2013

An unexpected bonus

Long-finned pilot whales, like other marine mammals in the Strait of Gibraltar, face a host of potential threats to their health and well-being.

What kind of risks do pilot whales face? A pilot whale with a large, fresh wound next to its dorsal fin

Traffic here in the Strait can be intense, with risks of ship or propeller strikes combined with elevated noise that may hinder the communication and foraging of these animals.

Heavy recreational fishing in the area adds risks of interactions with fishing gear, and industrial pollution of the Mediterranean waters poses risks of toxic compounds such as heavy metals building up across the food chain.

In addition, the whales have to navigate natural threats, and - just like the rest of us - they occasionally get sick.

The morbillivirus outbreak

Curro, a resident pilot whale of the Strait that was injured by a ship's propeller in May 2008, but is still going strong

From October 2006 and throughout April 2007, the population of pilot whales in the Western Mediterranean was hit hard by a massive morbillivirus outbreak. Cetacean morbillivirus is a virus closely related to canine distemper virus and also human measles, and it can be highly lethal.

A large part of the pilot whale population in this area disappeared over the course of the next handful of years. This has caused a lot of social restructuring, with most pilot whale groups reorganizing themselves by merging with other individuals. Fortunately, CIRCE has collected extremely valuable data over the last 13 years, documenting these changes as they were happening.

An unexpected bonus

As it turns out, the group we tagged on the 8th happens to be a truly exceptional study group: These animals have been observed consistently together over the course of the last 13 years that CIRCE has been operating, and have escaped relatively unscathed by the morbillivirus epidemic. The social interactions we observe in this group of animals will therefore be a valuable piece of information for understanding how pilot whales that have grown up together coordinate behaviors and interact with each other.